title: NLRP3 inflammasome activation results in hepatocyte pyroptosis, liver inflammation, and fibrosis in mice.
abstract: Inflammasome activation plays a central role in the development of drug-induced and obesity-associated liver disease. However, the sources and mechanisms of inflammasome-mediated liver damage remain poorly understood. Our aim was to investigate the effect of NLRP3 inflammasome activation on the liver using novel mouse models. We generated global and myeloid cell-specific conditional mutant Nlrp3 knock-in mice expressing the D301N Nlrp3 mutation (ortholog of D303N in human NLRP3), resulting in a hyperactive NLRP3. To study the presence and significance of NLRP3-initiated pyroptotic cell death, we separated hepatocytes from nonparenchymal cells and developed a novel flow-cytometry-based (fluorescence-activated cell sorting; FACS) strategy to detect and quantify pyroptosis in vivo based on detection of active caspase 1 (Casp1)- and propidium iodide (PI)-positive cells. Liver inflammation was quantified histologically by FACS and gene expression analysis. Liver fibrosis was assessed by Sirius Red staining and quantitative polymerase chain reaction for markers of hepatic stellate cell (HSC) activation. NLRP3 activation resulted in shortened survival, poor growth, and severe liver inflammation; characterized by neutrophilic infiltration and HSC activation with collagen deposition in the liver. These changes were partially attenuated by treatment with anakinra, an interleukin-1 receptor antagonist. Notably, hepatocytes from global Nlrp3-mutant mice showed marked hepatocyte pyroptotic cell death, with more than a 5-fold increase in active Casp1/PI double-positive cells. Myeloid cell-restricted mutant NLRP3 activation resulted in a less-severe liver phenotype in the absence of detectable pyroptotic hepatocyte cell death.
  
  
  CONCLUSIONS
  Our data demonstrate that global and, to a lesser extent, myeloid-specific NLRP3 inflammasome activation results in severe liver inflammation and fibrosis while identifying hepatocyte pyroptotic cell death as a novel mechanism of NLRP3-mediated liver damage.
authors.affiliation: Department of Pediatrics, University of California San Diego, La Jolla, CA; Department of Gastroenterology and Hepatology, University Hospital Essen, Essen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Wree
authors.forename: Akiko
authors.initials: A
authors.lastname: Eguchi
authors.forename: Matthew D
authors.initials: MD
authors.lastname: McGeough
authors.forename: Carla A
authors.initials: CA
authors.lastname: Pena
authors.forename: Casey D
authors.initials: CD
authors.lastname: Johnson
authors.forename: Ali
authors.initials: A
authors.lastname: Canbay
authors.forename: Hal M
authors.initials: HM
authors.lastname: Hoffman
authors.forename: Ariel E
authors.initials: AE
authors.lastname: Feldstein
mesh_terms: D000818:Animals; D018501:Antirheumatic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology*; D004195:Disease Models, Animal; D006130:Growth Disorders / Q000235:genetics / Q000276:immunology; D055166:Hepatic Stellate Cells / Q000276:immunology / Q000473:pathology; D006505:Hepatitis / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D022781:Hepatocytes / Q000276:immunology*; D006801:Humans; D058847:Inflammasomes / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D053590:Interleukin 1 Receptor Antagonist Protein / Q000494:pharmacology; D008103:Liver Cirrhosis / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D009504:Neutrophils / Q000276:immunology / Q000473:pathology; D017354:Point Mutation; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism
chemical_list: D018501:Antirheumatic Agents; D002352:Carrier Proteins; D058847:Inflammasomes; D053590:Interleukin 1 Receptor Antagonist Protein; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D017472:Receptors, Interleukin-1